Study calls for rethink on vehicle emissions tests

Emissions from the world’s fleet of cars, lorries and buses account for 38,000 premature deaths annually worldwide, claims a study co-authored by University of Colorado Boulder researchers.

Testing inefficiencies, maintenance inadequacies and other factors have led to 4.6 million tons more harmful nitrogen oxides (NOx) than standards allow, according to the study that has been published in Nature.

The findings are said to reveal major inconsistencies between what vehicles emit during testing and what they emit in the real world, a problem more severe that the Volkswagen incident of 2015 when it was found that millions of new diesel cars were fitted with so-called defeat devices.

The devices sense when a vehicle is undergoing testing and reduce emissions to comply with government standards. Excess emissions from defeat devices have been linked to about 50 to 100 US deaths per year, studies show.

“A lot of attention has been paid to defeat devices, but our work emphasizes the existence of a much larger problem,” said Daven Henze, an associate professor of mechanical engineering at CU Boulder who, along with postdoctoral researcher Forrest Lacey, contributed to the study. “It shows that in addition to tightening emissions standards, we need to be attaining the standards that already exist in real-world driving conditions.”

The research was conducted in partnership with the International Council on Clean Transportation, a Washington, D.C.-based nonprofit organization, and Environmental Health Analytics LLC.

For the paper, the researchers assessed 30 studies of vehicle emissions under real-world driving conditions in 11 major vehicle markets representing 80 per cent of new diesel vehicle sales in 2015. Those markets include Australia, Brazil, Canada, China, the European Union, India, Japan, Mexico, Russia, South Korea and the United States.

They found that in 2015, diesel vehicles emitted 13.1 million tons of NOx, an umbrella term for gases such as NO, NO2 and N2O, which are themselves toxic and are a chemical precursor to other toxic gases such as ozone. Exposure in humans can lead to heart disease, stroke, lung cancer and other health problems. Had the emissions met standards, the vehicles would have emitted closer to 8.6 million tons of NOx.

Heavy-duty vehicles were the largest contributor worldwide, accounting for 76 per cent of the total excess NOx emissions.

Henze used computer modelling and NASA satellite data to simulate how particulate matter and ozone levels are, and will be, impacted by excess NOx levels in specific locations. The team then computed the impacts on health, crops and climate.

“The consequences of excess diesel NOx emissions for public health are striking,” said Susan Anenberg, co-lead author of the study and co-founder of Environmental Health Analytics LLC.

China is said to suffer the greatest health impact with 31,400 deaths annually attributed to diesel NOx pollution, with 10,700 of those deaths linked to excess NOx emissions beyond certification limits. In Europe 28,500 deaths annually are attributed to diesel NOx pollution, with 11,500 of those deaths linked to excess emissions.

The study projects that by 2040, 183,600 people will die prematurely each year due to diesel vehicle NOx emissions unless governments act.

The authors said emission certification tests, both prior to sale and by vehicle owners, could be more accurate if they were to simulate a broader variety of speeds, driving styles and ambient temperatures. Some European countries now use portable testing devices that track emissions of a car in motion.

Commenting on the study, Dr Paul Young, lecturer and atmospheric Scientist, Lancaster Environment Centre, Lancaster University, said: “This work is a thorough assessment of the size of the gap between real world and lab-estimated emissions, showing that the former can be up to five times higher than the emission standard.

“This means more NOx, more particulate matter and more ground level ozone, all of which have bad effects on health, plants and even our buildings and infrastructure. One can quibble with the authors’ estimates of the impacts – and they do acknowledge the uncertainty – but they all point in one direction: more deaths and lower crop yields.

“This work points to the need to do two things: (1) get better real world estimates of vehicle emissions, and (2) have regulatory procedures that stipulate meeting real world driving emissions. This study has made great strides towards number 1), and – as the authors say – regulators are moving towards number (2).”

The 38,000 deaths figure was quoted a few weeks ago as 40,000 on the BBC and strongly implied just UK deaths rather than worldwide. Looks like environmentalists jumping on the emissions scandal bandwagon when the effect to health in the UK perhaps more marginal.

Nick – I don’t know what story you heard in BBC, but the number you are referring to (40,000 in the UK) was likely an estimate of the total number of deaths associated with all air pollution from any source in the UK. In contrast, our article is reporting the number of deaths occurring throughout the entire globe (not just the UK) associate with air pollution formed from just the fraction of NOx emissions from diesel vehicles that is above certification limits. This is a small fraction of total NOx emissions, and an even smaller fraction of the total amount of emissions that lead to formation of all air pollution (which globally is associated with about 3 million deaths per year world wide).

I realize all of these different stats can get confusing, and difficult to parse, but there’s no bandwagon or environmentalist conspiracy here. If you’re feeling concerned or confused about mixed messages, go on and ask a scientist! We’re glad to explain more — sensible and reasoned discussion is what we do for a living.

Noting the points from Dave Brook and Daven Henze, the real problem with the claimed massive death toll from pollution is that the meja like the scare numbers “40,000 deaths preventable” etc. They do not read the caveats and clarifications which show that these numbers are not going to be found on the street this year.

It is fair to say that the forecast mortality rates and reduction of lifespan are little more than statistical estimates with wide error ranges and many limitations in their scientific veracity. However, the risk is that a fear-campaign is started and draconian and costly measures are implemented to reduce public outrage which then achieve little or nothing that can be measured.

BATNEEC was a good principle in environmental improvement for many years and should continue to be the guide-rule. Despite all the pollution, I won’t hold my breath waiting for common sense to be applied!

No Critisism of the article was intended. Rather my concern is the dubious use of stats to support a point of view and avoiding looking at the bigger picture. The VW scandal has been capitalised upon and my fear is it will unjustly / disproportionately cost the average man on the street.

These estimated/simulated numbers of deaths are somewhat dubious. Air quality has been steadily increasing for many years in Europe. If you apply the values to the air quality in London during the ‘smog’ times or around old large industrial complexes you would have been stepping over bodies on the pavement.
There does not appear to be any mention of NOx emissions from any other source such as heating boilers.

Lots of fuss over emissions from road vehicles, but what about emissions from aircraft and from shipping? Aircraft dump tonnes of exhaust high in the atmosphere, and large ships burn 100’s of tonnes of heavy fuel oils a year, about which we hear no mention . . . Why?
It seems to me that rather than keep hammering the car manufacturers, we would be better concentrating on the greater sources of pollution production – shipping, airliners, power-plants, diesel trains, and HGVs – where fossil fuels are consumed in greater quantities.